Cancer Research UK scientists have discovered that women of African and West Indian descent who are struck down by the disease are diagnosed with it around 21 years younger than their white counterparts.

Results showed that the black patients contracted the disease at an average age of 46, while the white patients were diagnosed at an average age of 67.

The study authors looked at 102 black women and 191 white women diagnosed with breast cancer at Homerton University Hospital in Hackney, London, between 1994 and 2005 in the first major research of its kind.

The study also found that survival rate was poorer among black women and their tumours are more likely to be aggressive and unresponsive to new drugs like Herceptin.

If the results, published online in the British Journal of Cancer, are confirmed in larger studies then it could have implications for how black women are screened, treated and diagnosed in the future.

Dr Rebecca Bowen, the author of the study, said: “Twenty five per cent of all breast cancer cases diagnosed in London during the period studied were in women aged 45 or younger - but this figure rose to 45 per cent among the black population in Hackney.

“We think the differences in the way tumours of black and white women behave can be put down to the biological differences between the two ethnic groups.

"We’re now trying to find out why the tumours are so different so that we can develop new treatments to target the aggressive forms of breast cancer seen in young black women.”

Until recently, UK cancer registries have not collected ethnicity data, but American research has suggested that African-American women get breast cancer at a younger age and at a more advanced stage.

However, breast cancer among black British women is thought to be lower than in the white population.

Breakthrough Breast Cancer and Cancer Research UK today launched the first UK-based clinical trial to improve treatments for hormone and HER2 negative tumours, also known as “triple negative”.

The aggressive form of breast cancer is usually found in younger women and those of African ethnicity.

It is hoped that up to 450 women will take part over a five-year period.

The trial will compare the women’s responses to a platinum-based drug, carboplatin, which is not normally used to treat breast cancer, with docetaxel, the current treatment for hormone and HER2 negative tumours.